Macro typeface::choices

macro_rules! choices {
    ($(#[$attribute:meta])* pub $name:ident($type:ty) {
        $($value:expr => $variant:ident,)*
        _ => $other:ident,
    }) => { ... };
    ($(#[$attribute:meta])* pub $name:ident($type:ty) {
        $($value:expr => $variant:ident,)*
    }) => { ... };
    ($(#[$attribute:meta])* pub $name:ident($type:ty) {
        $($value:expr => $variant:ident($string:expr),)*
    }) => { ... };
}

Implement choices.